As a means of providing a color image excellent in sharpness a photographic light-sensitive material for forming an unsharp mask is proposed in French Patent No. 2,260,124, and Japanese Patent Application (OPI) No. 201,246/86. Such a photographic light-sensitive material consists of at least three layers. Particularly, such a photographic light-sensitive material has an essential layer structure comprising a lamination of a physically-developable nucleus-containing layer containing a nondiffusible coupler, a layer containing a scavenger of an oxidation product of a color developing agent, and a light-sensitive silver halide emulsion layer containing a nondiffusible coupler in this order. In this process, the photographic light-sensitive material which has been exposed to light is color-developed with a first color developing solution free of silver halide solvent to obtain a color negative image. The photographic light-sensitive material thus processed is then physically color-developed with a second color developing solution containing a silver halide solvent to obtain an unsharp positive image. However, it was found that this process has some unavoidable disadvantages. That is, it was found that since at least three layers are essential, it is difficult to provide a thin lamination of such a photographic light-sensitive material, reducing the effect of improving sharpness. Such a photographic light-sensitive material is also disadvantageous in that the requirement of two color developing steps complicates the development processing, increasing the cost and prolonging the processing time.
Furthermore, another technique for forming an unsharp mask is proposed in Japanese Patent Application (OPI) No. 169,843/76 (the term "OPI" as used herein means an "unexamined published application"). That is, a photographic light-sensitive material is proposed comprising at least two layers, i.e., as a first layer, a light-sensitive silver halide emulsion layer containing a nondiffusible coupler and, as a second layer, a layer containing a nondiffusible colored compound having the same series color as the hue of said coupler which undergoes reaction with an oxidation product of a developing agent so that the reaction product is eluted from the photographic layer upon development. In this process, when an oxidation product of a developing agent is formed in the light-sensitive silver halide emulsion layer containing a coupler, a part of the oxidation product diffuses into the second layer where it reacts with said nondiffusible colored compound present therein so that said nondiffusible colored compound is decolored to obtain an unsharp positive image. In this process, the degree of improvement in sharpness is related to the density and gradation of the unsharp positive image, and hence to the amount of the oxidation product of the developing agent diffused into the second layer. In order to increase the amount of the oxidation product of the developing agent diffused into the second layer, it is necessary to increase the amount of the oxidation product of the developing agent formed in the light-sensitive silver halide emulsion layer. However, it was found that the horizontal diffusion of the oxidation product of the developing agent cannot be ignored. That is, such a photographic light-sensitive material was found disadvantageous in that the more the amount is of the horizontal diffusion of the oxidation product of a developing agent, the more the expansion is of dye clouds formed by the coloring of the coupler present in the layer, thereby reducing the effect of the improving sharpness and deteriorating graininess.
Moreover, a further technique for forming an unsharp mask is proposed in Japanese Patent Application (OPI) Nos. 25,756/87 and 35,355/87. In this process, a dye which shows a proper diffusion during processing or an alkaline unstable precursor thereof and a nondiffusible coupler are used in combination. However, this process was found disadvantageous in that the dye diffuses not only during development but also during storage at a high temperature and humidity after formation of images, causing color stain.
Thus, all the conventional techniques for forming an unsharp mask leave much to be desired in practical sense. Thus, a perfect resolution has long been desired.